Scholars' Mine Masters Theses Student Theses and Dissertations Spring 2002 Glass transition behavior of thin poly(methyl methacrylate) films on silica Moses T. Kabomo Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Chemistry Commons Department: Recommended Citation Kabomo, Moses T., "Glass transition behavior of thin poly(methyl methacrylate) films on silica" (2002). Masters Theses. 2151. https://scholarsmine.mst.edu/masters_theses/2151 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. GLASS TRANSITION BEHAVIOR OF THIN POLY(METHYL METHACRYLATE) FILMS ON SILICA by MOSES TLHABOLOGO KABOMO A THESIS Presented to the Faculty of the Graduate School of the UNIVERSITY OF MISSOURI-ROLLA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN CHEMISTRY 2002 T8066 81 pages Approved by iii PUBLICATION THESIS OPTION This thesis has been prepared in the style utilized by the ACS journal Macromolecules. Pages 30-57 will be submitted for publication in that journal or one of ACS journals. Appendices A and B have been added for purposes normal to thesis writing. IV ABSTRACT Modulated Differential Scanning Calorimetry (MDSC) was used to study the glass transition behavior of poly(methyl methacrylate) (PMMA) adsorbed onto silica substrates from toluene. Untreated fumed amorphous silica and silica treated with hexamethyldisilazane were used for the adsorption to probe the effect of polymer- substrate interactions. To test the effect of molecular weight on the Tg of adsorbed polymers, low polydispersity PMMA samples of varying molecular weights were used. The results revealed a broadening of the glass transition towards high temperatures. The observed increase in the glass transition breadth varied with adsorbed amount and the type of silica used for the adsorption. Larger increases in the glass transition temperature and breadth, as high as 60 °C, were observed for PMMA films on untreated silica. The larger increase in Tg was attributed to restricted segmental motions due to H-bonding between PMMA carbonyls and the surface hydroxyls. The MDSC results were verified by Fourier Transform Infrared (FTIR) spectroscopy which showed a decrease in the bound fraction with increasing adsorbed amount for all the molecular weights studied. V ACKNOWLEDGMENTS I would like to thank my advisor Dr Frank D. Blum for the guidance and assistance he afforded me during my study. I would also like to thank my Advisory Committee members Dr James O. Stoffer and Dr Stephen L. Rosen. vi TABLE OF CONTENTS Page PUBLICATION THESIS OPTION..........................................................................................iii ABSTRACT.................................................................................................................................iv ACKNOWLEDGMENTS.......................................... v LIST OF ILLUSTRATIONS..................................................................................................viii LIST OF TABLES......................................................................................................................xi 1. INTRODUCTION.............................................................................................................. 1 2. BACKGROUND.................................................... 3 2.1. GLASS TRANSITION OF POLYMERS..............................................................,3 2.1.1. The Free Volume Theory............................................................................... 3 2.1.2. The Thermodynamic Theory.............,........................................................... 6 2.1.3. The Kinetic Theory..........................................................................................7 2.1.4. Factors that Influence Tg.............. 9 2.1.4.1 Molecular Weight................................. 10 2.1.4.2 Copolymerization............... 11 2.1.4.3 Cross-linking................................................................................... 11 2.1.4.4 Tacticity..............................................................................................12 2.1.4.5 Plasticizers.........................................................................................13 2.2. ADSORPTION OF POLYMERS ON SURFACES.............................................14 2.2.1. Polymer Chain Conformations.....................................................................15 2.2.2. Driving Force for Adsorption....................................................................... 17 vii 2.2.3. Formation of an Adsorbed Layer................................................................. 18 2.2.4. Conformation of the Adsorbed Layer.........................................................20 2.3. MODULATED DIFFERENTIAL SCANNING CALORIMETRY (MDSC)..21 2.4. REFERENCE................. 27 3. MDSC AND FTIR STUDY OF THE GLASS TRANSITION OF POLY (METHYL METHACRYLATE) ADSORBED ON SILICA..............................30 3.1. Abstract............................................................................ 30 3.2. Introduction.............................................................................................................. 30 3.3. Experimental............................................................................................................. 32 3.4. Results and Discussion.............................................................................................34 3.5. Conclusion.................................................................................................................52 3.6. Reference................................................................ 56 APPENDICES A. DETERMINATION OF ADSORBED AMOUNT BY THERMOGRAVIMETRIC ANALYSIS..........................................................................58 B. INFRARED SPECTROSCOPY OF PMMA THIN FILMS ON SILICA.................65 V IT A ..........................................................................................................................................70 viii LIST OF ILLUSTRATIONS Figure Page 2.1. Variation of (a) specific volume, and (b) isothermal expansion coefficient, α, and compressibility factor, β, with temperature.............................................................. 5 2.2. Effect of solvent on polymer chain dimensions.............................................................. 17 2.3. Spreading effects on adsorbed layer thickness................................................................20 2.4. The loop-tail-train model of an adsorbed polymer........................................................ 20 2.5. MDSC heating profile with an underlying heating rate of 2.5 °C/minute, a modulation period of 60 seconds, and a modulation period of ±1 °C.......................... 24 2.6. MDSC data for a PMMA sample showing the complex raw data and the deconvoluted heat flow curve........................................................................................... 25 2.7. MDSC data for a PMMA sample showing the total heat flow and its two components, the reversing heat flow and the non-reversing heat flow........................26 3.1. MDSC curves (derivative of the reversing heat flow) of bulk PMMA samples. The Tg’s are taken as the peak maxima............................................................................ 35 3.2. MDSC curves of bulk P19MMA and P19MMA adsorbed on M5 from 5 mg/mL (solid) and 10 mg/mL (dash) solutions.............................................................................36 3.3. MDSC curves of bulk P49MMA and P49MMA adsorbed on M5 from 5 mg/mL (solid) and 10 mg/mL (dash) solutions.............................................................................37 3.4. MDSC curves of bulk P216MMA and P216MMA adsorbed on M5 from 5 mg/mL (solid) and 10 mg/mL (dash) solutions.............................................................. 38 3.5. FTIR spectra of bulk PMMA and P19MMA adsorbed on M5 in the region of the carbonyl absorption............................................................................................................ 45 ix 3.6. FTIR spectra of bulk PMMA and P49MMA adsorbed on M5 in the region of the carbonyl absorption............................................................................................................46 3.7. FTIR spectra of bulk PMMA and P216MMA adsorbed on M5 in the region of the carbonyl absorption.......... ...........................................................................................47 3.8. FTIR spectra of bulk PMMA and P587MMA adsorbed on M5 in the region of the carbonyl absorption..................................................................................................... 48 3.9. MDSC curves of PMMA adsorbed on TS530 from 10 mg/mL solutions.................. 53 3.10. FTIR spectra of bulk PMMA and PMMA adsorbed on TS530 in the region of the carbonyl absorption......................................................................................................54 A.l. Determination of the adsorbed amount by TGA. The sample was ramped from ambient temperature to 600 °C at a heating rate of 10 °C/min..................................... 60 A.2. TGA curves for the determination of adsorbed amount of P19MMA-0.8 and P19MMA-1.8. The samples